1. Field of the Invention
The present invention relates generally to apparatus for setting doors to vehicle bodies in vehicle body assembly lines, and more particularly, to a door setting apparatus provided at a door mounting station in a vehicle body assembly line and employing a robot for picking out one of doors sorted on a plurality of pallets, which is fit for a vehicle body conveyed or being to be conveyed to the door mounting station, and for setting automatically the selected door to a door supporting portion of the vehicle body staying at the door mounting station.
2. Description of the Prior Art
In a previously proposed vehicle body assembly line, a door which is to be mounted on a vehicle body conveyed into a door mounting station is supplied from a door delivering apparatus to a door setting device so as to be set thereby to the vehicle body staying at the door mounting station and then the position of the door set to the vehicle body is adjusted by one or more workers so that the door is put properly on a door supporting portion provided on the vehicle body, as disclosed in, for example, the Japanese patent application published after examination with the publication No. 57/48334 on Oct. 15, 1982. This means that the door setting process at the door mounting station in the vehicle body assembly line has been partially automatized and still includes some work being out of the mechanical control, such as adjustment of the position of the door in relation to the door supporting portion of the vehicle body, and therefore it is desired that the door setting process is much more automatized or advanced in reduction of labor. Accordingly, it has been proposed to introduce an industrial robot, which has been recently spread in various fields of industry, especially, in the manufacturing industry, into the door mounting station in the vehicle body assembly line for setting automatically the door to the door supporting portion of the vehicle body, and a playback robot of the articulated type which operates with a predetermined working path and is capable of being used at the door mounting station in the vehicle body assembly line has been developed.
However, in the case where the vehicle body assembly line is so arranged that a plurality of vehicle bodies of several different kinds are assembled therein and the vehicle bodies of several differents kinds conveyed successively to the door mounting station therein are provided with respective doors at the door mounting station, or the vehicle body assembly line is so arranged that a plurality of vehicle bodies of a single kind are assembled therein and each of the vehicle bodies of a single kind conveyed successively to the door mounting station therein is provided with two or more different doors, for example, front and rear doors at the door mounting station, and such a robot as mentioned above is used for setting automatically each door to a corresponding door supporting portion provided on the vehicle body staying at the door mounting station, there are the following problems.
In the vehicle body assembly line wherein the doors of plural different types are selectively and automatically set to the vehicle bodies by the robot at the door mounting station, the doors are sorted on plural pallets each making a group of doors of the same type and one of the sorted doors which is selected in accordance with the vehicle body conveyed to the door mounting station is picked out by the robot and then set to a corresponding door supporting portion of the vehicle body staying at the door mounting station through the movement of the robot. Each of the pallets used for sorting the doors in such a vehicle body assembly line as mentioned above, which may be required to be capable of holding any of the doors of plural different types and also to be movable, is usually formed with not so high dimensional precision. Further, the doors put on the pallet are loosely held thereby so as to be easily and smoothly removed therefrom by the robot. Accordingly, the position of each of the pallets or the position of each of the doors sorted on the pallets tends to be undesirably dislocated from a predetermined working path of the robot.
Under such conditions, if the position of the pallet or the position of each of the doors on the pallet is dislocated from the working path of the robot, the robot may hold the selected door in an improper manner and as a result the selected door may not be set properly to the door supporting portion of the vehicle body.
Further, if the vehicle body conveyed into the door mounting station is caused to stay at a position deviated from a predetermined regular position in the door mounting station due to, for example, positional deviation of the vehicle body from a regular position on a conveyer in the vehicle body assembly line, the robot may not set properly the selected door held thereby to the door supporting portion of the vehicle body staying at the door mounting station.